This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A127997 #16 Mar 14 2016 05:01:54 %S A127997 2,5,79,101,359,857,4463,9029,27823 %N A127997 Numbers n such that (22^n - 1)/21 is prime. %C A127997 9029 is a term found by Richard Fischer in 2004. - _Alexander Adamchuk_, Feb 11 2007 %C A127997 No other terms < 100000. - _Robert Price_, Feb 25 2012 %H A127997 H. Dubner, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1185243-9">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930. %H A127997 H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a> %H A127997 <a href="/index/Pri#primepop">Index to primes in various ranges</a>, form ((k+1)^n-1)/k %t A127997 Select[Prime[Range[100]],PrimeQ[(22^#-1)/21]&] %o A127997 (PARI) isok(n) = isprime((22^n-1)/21); \\ _Michel Marcus_, Mar 13 2016 %K A127997 hard,more,nonn %O A127997 1,1 %A A127997 _Alexander Adamchuk_, Feb 11 2007 %E A127997 More terms from _Ryan Propper_, Mar 29 2007 %E A127997 27823 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008